A Silicon steel, ferrite, amorphous alloy, Fe-based nano-crystalline alloy material and the like have been known as magnetic materials having a high saturation magnetic flux density and excellent AC magnetic properties, that are used in various transformers, reactor choke coils, noise suppression parts, laser power supplies, pulse-power magnetic parts for accelerators, various motors, various generators and the like.
While a silicon steel plate is manufactured from an inexpensive material and has a high magnetic flux density, there is a problem of high core loss in high-frequency applications. It is extremely difficult to process these materials as thin as amorphous thin ribbons because of its production process. Further, it has a high eddy-current loss and thus a high loss associated therewith. Thus, it is disadvantageous. In addition, a ferrite has a low saturation magnetic flux density and poor temperature properties. Thus, the ferrite is not suitable for high-power applications where a high operational magnetic flux density is applied, since it easily magnetically saturates.
A Co-based amorphous alloy has a problem of thermal instability since its saturation magnetic flux density is as low as 1 T or less for its practical material. This causes some problems that a part becomes large and a core loss increases due to changes with ages when it is used in high-power applications. Moreover, there is an economical problem since Co also is expensive.
A Fe-based amorphous soft magnetic alloy as described in JP-A-5-140703 has very good soft magnetic properties, since it has a good squareness property and a low coercive force. However, the saturation magnetic flux density of the Fe-based amorphous soft magnetic alloy is determined by balancing between the atomic distance and the coordination number and Fe concentration, and thus a physical upper limit thereof is about 1.65 T. In addition, the Fe-based amorphous soft magnetic alloy has problems that its property is deteriorated due to a stress since it has high magnetostriction, and that it causes high noise in applications where currents in the audible frequency range are superposed. Moreover, If Fe is significantly substituted with other magnetic element such as Co or Ni, a slight increase in saturation magnetic flux density is also found in a conventional Fe-based amorphous soft magnetic alloys. However, the amount (percent by weight) of the element is desirably minimized in terms of cost. Because of these problems, a soft magnetic material having nano-crystal, as described in JP-A-1-156451, has been developed and used in various applications.
As a soft magnetic compact having a high magnetic permeability and a high saturation magnetic flux density, a technique as described in JP-A-2006-40906 has also been disclosed but its saturation magnetic flux density has not yet reached 1.7 T. Thus, a magnetic alloy having a saturation magnetic flux density equal to or greater than that value is demanded.
PATENT DOCUMENT 1: JP-A-5-140703
PATENT DOCUMENT 2: JP-A-1-156451
PATENT DOCUMENT 3: JP-A-2006-40906